From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: To: 9fans@9fans.net From: erik quanstrom Date: Fri, 13 Jun 2008 20:39:48 -0400 MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Subject: Re: [9fans] I/O load crashes Qemu Topicbox-Message-UUID: c06a43c4-ead3-11e9-9d60-3106f5b1d025 > On a T42 running FreeBSD, a stock FreeBSD-4.11/qemu gets > 18MB/s & plan9/qemu gets 3MB/s. Both tested by writing 100MB > from /dev/zero to a file. Neither needs any special drivers. > > I think part of the performance problem is qemu emulates an > early Intel ATA controller chip (PIIX3) and perhaps plan9 > does not do certain optimizations. It would not be too hard > to emulate a more modern controller. try turning dma on. it is very unlikely that plan 9 is missing some important ata optimization. > IMHO a virtualizable processor is the necessary first step as > it clears one's mind about what not to do in an efficient > virtualizable IO architecture! unless you are contemplating a processor with i/o instructions, what does the processor have to do with i/o architecture? > Emulating grotty device > registers with horrible side-effects is just too painful and > one would be forced to abstract that out. Probably too late > for that! i find there's a certain simplicty in dealing directly with hardware, provided one has documentation. but just wait, there will come a day when people complain about the nasty registers in vm and how it would be good to abstract that stuff out. i think that may have been yesterday. - erik